290 KANSAS UNIVERSITY SCIENCE BULLETIN. 



instances the cell was packed ; sometimes I would find a fair- 

 sized space above the caterpillars. 



All of the caterpillars that I took from nests of 0. dorsalis 

 showed signs of life. The abdominal segments invariably re- 

 sponded to stimulation. However, I found none as active as 

 some stored by 0. papagorum and 0. arrcnsls. 



The egg was usually suspended from the ceiling of the cell 

 by a white thread, sometimes as long as the egg itself. In an 

 exceptional case the egg was on a caterpillar, being attached 

 bj^ a thread to its seventh abdominal segment. This caterpillar 

 was on the bottom of the cell and was probably the first one 

 stored. 



Although attached to the ceiling, the egg is not always su- 

 spended above the caterpillars. It was only in exceptional 

 cases — in unusually large cells — that I found it so. I have 

 found it hanging among the caterpillars. Usually I could not 

 find the egg at all until some of the caterpillars had been re- 

 moved. 



The time of oviposition, in relation to the storing of the nest, 

 probably varies. On one occasion I noted a wasp back into its 

 cell after it had been stored, supposedly for oviposition, and 

 just before it had been sealed up. I concluded then that ovi- 

 position takes place after the storing of the caterpillars. My 

 conclusion was upset when I saw a wasp back into a new cell 

 in which nothing had yet been stored. Several times I found 

 eggs suspended in cells only partially stored, and twice in cells 

 that were entirely empty. I also opened a number of empty 

 cells in which I found no egg. 



The egg of 0. dormlis is ellipsoidal and rounded at the ends. 

 Its length is about 4.5 mm. and its greatest diameter is 1.5 mm. 

 It was more nearly flattened at the end of attachment to the 

 thread. It was also less rounded on one side than on another. 

 Its shape reminded me of that of a cucumber. In color the 

 egg was creamy white. The thread attachment was white and 

 about the same length as the egg. 



But one 0. dorsalis grub came under my observation. Mr. 

 Williams saw a wasp closing its nest on the afternoon of 

 August 7. He marked the place and showed it to me. Five 

 days later I opened the nest. It had one cell containing seven 

 caterpillars and a grub, which I should judge was about one- 

 third grown. In appearance this grub was like those of other 



